Half-Life

Date: 06/24/2001 at 15:40:14
From: Joe DeMarco
Subject: Half Lives
Please help me; I do not know what a half life is. Can you explain it
to me in simple terms?
Thanks a bunch,
Joe

Date: 06/26/2001 at 10:19:22
From: Doctor Roy
Subject: Re: Half Lives
Hello,
Half-life involves radioactive isotopes of elements.
Take the radioactive isotope of Carbon known as carbon-14. The half-
life of carbon-14 is around 5700 years. This means that in 5700 years,
only half of our original sample of carbon-14 will be left. Imagine
that we started with 256 g of carbon-14; in 5700 years, we will be
left with 128 g of carbon-14.
Further, in another 5700 years (or 11400 years from our starting
point), we will be left with 64 g (or half of 128g) of carbon-14.
Then in another 5700 years (or 17100 years from the starting point),
we will have 32 g (or half 64 g) of carbon-14.
This process continues until the isotope disappears completely. It is
actually a very efficient way of dating ancient remains and records
from the last 20000 years or so. Several artifacts have been dated in
this manner.
All radioactive isotopes have a half-life. The half-life ranges from
picoseconds for the latest elements created in the lab, to billions of
years in the case of uranium. In fact, it is uranium dating that is
used to date remains from the time before people were even on the
earth.
I hope this helps.
- Doctor Roy, The Math Forum
http://mathforum.org/dr.math/